U.S. Pat. No. 5,738,415 discloses a cutting tool that has a holder block assembly that includes a holder block and a sleeve removably mounted in the holder block for holding a cutter bit. The sleeve has a shank that is received in a hole in the holder block that extends along an axis. An interference fit between the outer surface of the shank and the wall of the holder block hole resists rotation of the sleeve when held in the holder block.
The outer surface of the shank and the holder block wall each has a larger diameter portion and a smaller diameter portion that extend axially along the axis and are separated by a transition area. The transition area is generally shaped as a conical frustum (that is, shaped as a truncated cone). A hydraulic line extends into the holder block and discharges into the transition area.
To remove the sleeve from the holder block, the hydraulic line is connected to a source of pressurized hydraulic fluid. The fluid exerts an axial force on the sleeve that axially displaces the sleeve with respect to the holder block.
The hydraulic system disclosed in the '415 patent works well to readily and quickly extract the sleeve from the holder block, but it does have disadvantages. The sleeve must move axially the entire distance of the larger diameter portion to extract itself from the holder block. When the sleeve is extracted, hydraulic fluid is released from the holder block. The released fluid may require cleanup or containment.
Thus there is a need for an improved holder block assembly that enables the sleeve to be extracted from the holder block with relatively short axial movement of the sleeve relative to the holder block, and without the release of hydraulic fluid.